Subject TIB_Connection.AlterUser() fails on IB6 classic/Linux?

I am writing an admin tool for my app, which must be able to create
users on an IB6 server. I use TIB_Connection.AlterUser(), and this
perfectly on Win32 based IB6.

However, when I try the same on Linux based IB6 classic server, I get

I/O error for file "isc4.gdb"
Error while trying to open file
No such file or directory

The same error occurs when I use "Users" of an TIB_UtilityBar.
Normal accesses to the Database (once I have installed my user
on the Linux box with "gsec") works ok, except, as it seems right
now, Server Events (they crash the app). But that's probably
another story...

Any idea what could be wrong?

Lukas Zeller (luz@...)